Add required 'begin' config support for microbatch models

[MichelleArk]

Resolves #10701

Problem

We need to know what the "beginning of time" is for a microbatch model, to know when to start for these two cases:

• The first time this model is run
• If you run in “full-refresh-mode”

This is distinct from the CLI parameter --event-time-start which can also be used when running in "incremental" mode.

Solution

• continue to return early if --event-time-start is provided
• For non-incremental runs (or if there is no checkpoint to lookback from), return the begin config! (raise exception if its not available, and further parse-time validation will be introduced as part of Microbatch Config Validation #10752
• update schemas.getdbt.com v12 manifest
• update tests to provide begin config.

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.04%. Comparing base (db69473) to head (9e0f684).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10756      +/-   ##
==========================================
+ Coverage   88.97%   89.04%   +0.06%     
==========================================
  Files         181      181              
  Lines       22956    22984      +28     
==========================================
+ Hits        20424    20465      +41     
+ Misses       2532     2519      -13     

Flag	Coverage Δ
integration	86.28% <88.88%> (+0.13%)	⬆️
unit	62.39% <88.88%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	62.39% <88.88%> (-0.05%)	⬇️
Integration Tests	86.28% <88.88%> (+0.13%)	⬆️

[MichelleArk]

CI should pass once dbt-labs/schemas.getdbt.com#57 is merged

[QMalcolm]

Woooo! This looks great 😄 I made one comment on updating a doc string, and we should probably fix it before merging, but also didn't want my review to be blocking as you'll be back online before I am.